The invention is related to the field of dense wavelength division multiplexing (DWDM) for fiber optic communications systems; more particularly, this invention is related to non-blocking wavelength routers and reusing wavelengths.
Wavelength routers are being used widely today in optical systems. The current methods used to implement wavelength router functionality can be classified into two different categories based on the technique they employ to perform the wavelength routing. One of the two technique relies on an Optical-to-Electrical-to-Optical (OEO) conversion process, where an input signal carried by a specific wavelength carrier on an input fiber, is demultiplexed, converted to an electrical signal by a photo detector and electronic circuitry, and then switched electronically to the input of a wavelength specific optical transmitter that is associated with potentially one of several wavelength specific fiber optic multiplexer ports driving a specific output fiber. One of the problems with this approach is that with current technology, one needs a plethora of lasers to perform the routing function. Each port of an optical multiplexer that serves an output fiber needs its own wavelength-matched laser, and each laser needs its own high power consumption, temperature stabilization circuit. Furthermore, in high reliability applications, the 1+1 protection optics double laser cost and power consumption. Providing spares is extremely costly for this approach since the likelihood of a failure is independent of the wavelength of the laser.
The other widely used technique, which is still the subject of much development, attempts to achieve both bit rate and signal format transparency by reducing the amount of electronics in the signal path. The ultimate vision then is called the xe2x80x9cAll Optical Networkxe2x80x9d or AON. In the AON, tunable lasers, tunable filters and optical switches replace their electronic counterparts. In a typical wavelength router implementation using these tunable lasers and filters and optical switches, the outputs of modulated tunable lasers drive the input side of an optical switch that interconnects the signal to the appropriate output fiber by way of a wavelength multiplexer. While this approach achieves bit rate and signal format independence, and addresses the issue of spares as well, it does little if anything to reduce cost and component count.
Also noteworthy is that in both of the approaches discussed above, an independent data stream modulates each laser or wavelength.
An apparatus comprising a comb generator and multiple modulators is described. In one embodiment, the comb generator generates a multi-wavelength comb of optical frequencies. Each of the modulators receives the comb on one input as well as an input data signal on another input. Each of the modulators modulates the comb with its input data signal, thereby creating a modulated comb signal having duplicate signal sidebands on each spectral line of the comb. Each modulator outputs the modulated comb signal on the output.